Vegetative roofing systems

ABSTRACT

Vegetative systems are described. In one embodiment, a vegetative system has substantially distinct or separate zones or layers in which each zone or layer performs primarily one of the functions of water retention, a growth medium for vegetation, and weed suppression. An upper may comprise coarse aggregate and serve the primary function of weed suppression; a middle layer may comprise a mixture of coarse aggregate, fine aggregate, and fine organic material and serve primarily as a growth medium for vegetation; and a lower layer may comprise high-density hygroscopic material and serve the primary function of water retention.

FIELD OF THE DISCLOSURE

The present invention generally relates to vegetation systems for roofsand other artificial and natural surfaces and methods of assemblingvegetation systems.

BACKGROUND

The term “green roof” is often used to describe a roof or similarsurface that has been adapted to facilitate vegetative growth.Accordingly, a green roof system will employ a vegetative system thatincludes growth media and, typically, features to permit water thatpermeates the system to drain from the roof.

Traditional green roof systems rely on aggregate particle sizedistribution (PSD) as the primary means of retaining storm water. Thestandards for PSD originate with the FLL guidelines. FLL guidelines aregreen roof standards developed by the German Research Society forLandscape Development and Landscape Design (also known asForschungsgesellschaft Landschaftsentwicklung Landschaftsbau e.V.).Generally the FLL guidelines call for an even-graded PSD to createapproximately 35% void space, which is distributed between macroporesand micropores. Micropores have a higher water retention capacity thanmacropores. Use of greater micropores requires a denser media (i.e., agreater proportion of small particle sizes), which adds weight to thesystem. Medias compliant with FLL guidelines weigh approximately 6-8lbs/f² per inch of system depth when fully saturated. These mediasretain up to 0.3 inches of rain per 1-inch of thickness, an efficiencywhich decreases as thickness increases. For example, a 4-inch green roofwith FLL-compliant media will retain approximately 1 inch of stormwater, whereas doubling the thickness to 8 inches will yieldapproximately 1.5 inches of storage. A 4-inch thick green roof compliantwith FLL guidelines weighs approximately 28 lbs/f², of which onlyapproximately 5 lbs, or 20% of the saturated weight, is water.

Furthermore, current vegetative systems used in green roofs may requiresignificant maintenance to inhibit weed growth or promote growth of thedesired vegetation and are inefficient storm water retention devices.

SUMMARY OF THE DISCLOSURE

Among the various aspects of the present disclosure is the provision ofvegetative systems having substantially distinct or separate zones orlayers in which each zone or layer performs primarily one of thefunctions of water retention, a growth medium for vegetation, and weedsuppression. Other beneficial properties are found in vegetative systemsof the present disclosure.

Briefly, the present disclosure is directed to a vegetative system,e.g., for use in constructing a green roof or other vegetation zone,that includes a freely draining, weed-suppressing upper layer; a middlenutritive layer; and a water retention lower layer. In a particularembodiment, the upper layer consists primarily of coarse aggregate; themiddle layer consists primarily of a mixture of coarse aggregate, fineaggregate, and fine organic material; and the lower layer consistsprimarily of high-density hygroscopic material.

In one particular embodiment, the middle nutritive layer and the upperweed suppression layer are applied as a single layer that separates overtime into substantially separate nutritive and weed suppression layers.In another embodiment, the nutritive and weed suppression layers areapplied separately. In yet another embodiment, materials that, overtime, will comprise the nutritive layer are initially applied on top ofthe weed suppression layer.

Plants, a filter layer, an air layer, a protection layer, a rootbarrier, or other gardening elements, such as stepping stones, edging,or gravel borders may be included certain embodiments of vegetativesystems of the present disclosure. In other embodiments, a vegetativesystem includes support structures, such as supporting elements to holdvegetative elements onto a sloped roof.

Although the vegetative system is largely described in terms ofsubstantially separate zones or “layers”, the layers may interact withone another and transition zones may form at the intersection of layers.For example, some portion of the nutritive layer may settle into thewater retention layer, the nutritive layer and the weed suppressionlayer may mix at the intersection of the layers, or the nutritive layerand the weed suppression layer may not fully separate into entirelydistinct layers (e.g., in an embodiment in which the nutritive and weedsuppression layers are applied as a composite layer, as discussedbelow). Additionally, as plants grow within the vegetative system, plantstructures will be included within one or more layers or may extend rootmass into all three layers. Furthermore, although the layers aregenerally described as a lower water retention layer, a middle nutritivelayer, and an upper weed suppression layer, materials (e.g., layers) maybe interposed between these layers. For example, a filter layer may beprovided between one or more of the water retention, nutritive, and weedsuppression layers.

Other objects and features will be in part apparent and in part pointedout hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of an exemplary embodiment of a vegetativesystem of the disclosure.

FIG. 2 is an illustration of another exemplary embodiment of avegetative system of the disclosure.

FIGS. 3-9 are graphs illustrating particle size distribution ofcomponents of vegetative systems of exemplary embodiments of thedisclosure.

FIG. 10 is an illustration of a further exemplary embodiment of avegetative system of the disclosure.

DETAILED DESCRIPTION

It must be noted that, as used in this specification and the appendedclaims, the singular forms “a,” “an” and “the” include plural referentsunless the content clearly dictates otherwise.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which the disclosure pertains. Although a number of methodsand materials similar or equivalent to those described herein can beused in the practice of the present disclosure, the preferred materialsand methods are described herein.

All numbers expressing quantities of ingredients, constituents, and soforth used in the specification and claims are to be understood as beingmodified in all instances by the term “about.” Notwithstanding that thenumerical ranges and parameters setting forth the broad scope of thesubject matter presented herein are approximations, the numerical valuesset forth in the specific examples are reported as precisely aspossible. All numerical values, however, inherently contain certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements.

Vegetative systems comprising storm water mitigation features andmethods of assembling such systems are described. In the followingdescription, for purposes of explanation, numerous specific details areset forth in order to provide a thorough understanding of variousexemplary embodiments. It will be evident, however, to one of ordinaryskill in the art that embodiments of the invention may be practicedwithout these specific details.

Vegetative Systems

FIG. 1 illustrates an exemplary embodiment of a vegetative system 100 ofthe invention. The vegetative system 100 includes a lower waterretention layer 102, a middle nutritive layer 104, and an upper weedsuppression layer 106.

Water Retention Layer

The water retention layer 102 of a vegetative system 100 may servemultiple functions related to water retention. It may prevent stormwater runoff, store water for future use by plants, or allow water toevaporate fairly readily to prevent pooling or root rot.

The water retention layer 102 comprises one or more materials orstructures that absorb or otherwise retain water. In certainembodiments, a material of the water retention layer holds water insuspension substantially throughout its volume and allows horizontaltransmissivity.

In one embodiment, for example, the water retention capacity of thewater retention layer (expressed as a percentage of volume) is at least60% (e.g., 60%, 65%, 70%, 75%, 80%, 85%, 90%, 93%, 94%, 95%, 96%, 97%,98%, 99%, or 100%). In another embodiment the water retention capacityis at least 80%. In yet another embodiment, the water retention capacityis at least 90%. Another alternative embodiment includes a waterretention layer with a water retention capacity of at least 95%.

For purposes of this disclosure, references to measurements of “waterretention capacity” of a vegetative system or component of a vegetativesystem (e.g., a water retention layer) refers to water retentioncapacity measured according to the following steps: (1) a one-footsquare section of the system or system component to be measured isweighed and then placed into a container; (2) a quantity of watersufficient to fully submerge the section of the system or systemcomponent is added to the container; (3) after 24 hours, the section ofthe system or system component is removed from the container and placedon a screen or other surface that will permit water to drain from thesection of the system or system component (or, alternatively, the wateris allowed to drain from the container); (4) the section of the systemor system component is left on the screen or other draining surface forone hour; and (5) measurements (e.g., saturated weight) of the drainedsection of the system or system component are taken. Comparisons betweenthe measurements of the dry material and the drained material may usedto identify measurements of water retention capacity. For example, thewater retention capacity of a system or system component, expressed as apercentage of volume, may be determined by subtracting the dry weightfrom the saturated weight and using that difference to derive the waterretention capacity, by volume, of a system or system component. Thefollowing illustrates one method of making this calculation (usingexperimental data for a water retention layer of an example embodimentof a vegetative system):

A 12-inch by 12-inch sample of a 1-inch thick system or system componenthas a dry volume of 144 cubic inches. 144 cubic inches equals 0.623gallons.

In an example, a 12-inch by 12-inch by 1-inch sample of a waterretention layer weighs 0.69 pounds when dry and 5.31 pounds whensaturated according to the steps listed above. That sample is retaining4.62 pounds of water (5.31−0.69=4.62).

1 gallon of water typically weighs 8.35 pounds. Using this weight, 4.62pounds of retained water is approximately equivalent to 0.55 gallons ofretained water (4.62/8.35=0.55).

In this example, 0.55 gallons of retained water equates to a waterretention capacity of the water retention layer sample of 88% of its dryvolume (0.55/0.623=0.88).

Other empirical measurements taken during a process similar to theprocess described above (e.g., of the volume of water added at step 2and/or the volume of water drained at step 4) may be used to determineor approximate characteristics of the system or system componentsubjected to such process.

The water retention layer 102 may be further defined by its waterretention under compression. In one embodiment, the water retentioncapacity under 100 pounds of compression is at least 80% of itsuncompressed water retention capacity (e.g., 80%, 85%, 90%, 93%, 95%,96%, 97%, or 98%). As discussed below, preferred materials forvegetative systems retain water under compression. In other embodiments,support structures, such as support beams, may be employed within awater retention layer to bear some or all of a compressive load that maybe imposed upon the water retention layer (e.g., the weight of the upperlayers and any additional weight, such as foot traffic), therebyincreasing the water retention capacity under compression above thelevel provided by the absorptive materials of the water retention layer.

References to “water retention under compression” refer to calculationsmade in connection with a process like the process used to determinewater retention capacity, described above, except that in step 3,compressive force is applied to the system or system component as itdrains. For example, to determine water retention capacity under 100pounds of compression, 100 pounds of force is applied to the system orsystem component during the draining step 3 (e.g., by placing a 100pound weight on top of the system during such step).

Other characteristics of a water retention layer are its saturatedweight and its dry weight. In certain embodiments, the saturated weightof the water retention layer of a vegetative system is equal to or lessthan 60 lb/ft² (e.g., 60 lb/ft², 56 lb/ft², 50 lb/ft², 45 lb/ft², 40lb/ft², 35 lb/ft², 30 lb/ft², 25 lb/ft², or 20 lb/ft²). In certainpreferred embodiments, the saturated weight of the water retention layerof a vegetative system is equal to or less than 30 lb/ft². In an exampleembodiment, the saturated weight of the water retention layer isapproximately 15 lb/ft².

A low dry weight to saturated weight ratio is preferred for someembodiments of water retention layers of vegetative systems of thedisclosure. In certain embodiments, the dry weight of the waterretention layer is 20% or less (e.g., 20%, 18%, 15%, 13%, 10%, or lessthan 10%) than its saturated weight. In some embodiments, the dry weightof the water retention layer is less than 15% of the saturated weight ofthe water retention layer.

In certain embodiments, the water retention layer includes rock wool(also known as mineral wool). In some preferred embodiments, the rockwool is high density post-industrial rock wool. In some embodiments, thewater retention layer of a vegetative system comprises rock wool with adensity in the range of 4 lb/ft³ to 16 lb/ft³ (e.g., 4 lb/ft³, 6 lb/ft³,8 lb/ft³, 10 lb/ft³, 12 lb/ft³, 14 lb/ft³, or 16 lb/ft³). In certainpreferred embodiments, the water retention layer of a vegetative systemcomprises rock wool with a density in the range of 8 lb/ft³ to 16lb/ft³.

In one example vegetative system embodiment, the water retention layercomprises rock wool with a density of 8 lb/ft³ which holds approximately90% of its volume in water; the weight of the retained water isapproximately equal to ten times the dry weight of the rock wool. Inthis embodiment, if supersaturated, the water flows horizontally withinthe water retention layer, e.g., toward roof drains; when notsupersaturated, the water remains within the layer until it is utilizedby plants or evaporates. In this embodiment, the water retention layerdries rapidly. This rapid drying creates a high ambient rechargecapacity, allowing the vegetative system layer to handle closely spacedstorm events. The peak flow reduction characteristics of this embodimentare increased, relative to current vegetative systems, due to alengthened hydraulic resistance time.

In an experiment, the transmissivity of a saturated one foot squarewater retention layer composed of a one inch thick section of rock woolwith a density of 8 lb/ft³ with an applied lateral load of 100 lb/fe wasmeasured at 0.05 gallons per minute at a slope of a quarter inch rise toa foot run, applying the ASTM D-4716 standard test (the Standard TestMethod for Determining the (In-plane) Flow Rate per Unit Width andHydraulic Transmissivity of a Geosynthetic Using a Constant Head).

Preferred materials for a water retention layer are polymeric orinorganic. In addition to rock wool, other polymeric or inorganicmaterials that may be used in the water retention layer of a vegetativesystem, include, by way of example, post-industrial non-woven fibers,such as industrial felt (also known as capillary fabric), othernon-woven geotextiles, microporous insulation board, open cell ceramicfoams, high density melamine foam, glass wool board, high density opencell polyurethane foam board, and other materials that exhibit one ormore characteristics of a water retention layer of the vegetativesystems of the present disclosure. In an example embodiment of avegetative system, the water retention layer comprises industrial feltwith a water retention capacity in the range of 60 to 80%. In apreferred embodiment, at least ninety five percent (95%) of thematerials comprising a water retention layer are polymeric or inorganic.

In some embodiments, the water retention layer includes a filter fabricor other separation feature either at or near the top of the waterretention layer (e.g., to serve as a filtering barrier between thenutritive (or composite layer) and the water retention layer) or at ornear the bottom of the water retention layer (e.g., to serve as afiltering barrier, or, alternatively a more complete barrier, betweenthe water retention layer and other protective membranes, roofingstructures, and the like), or both. In one embodiment, a filter fabricwith the characteristics listed in Table 1, below, is provided at thetop of the water retention layer (e.g., just below the nutritive (orcomposite layer)).

TABLE 1 Minimum Average Value (and Characteristic Measurement Standard)Unit Weight 4 oz/SY (ASTM D-3776) Grab Tensile Strength 100 lbs (ASTMD-4632) Grab Elongation 50% (ASTM D-4632) CBR Puncture Strength 300 lbs(ASTM D-6241) Mullen Burst Strength 200 psi (ASTM D-3786) TrapezoidalTear 30 lbs (ASTM D-4533) Apparent Opening Size (AOS) 0.212 mm (ASTMD-4751) Permittivity 1.7 sec-1 (ASTM D-4491) Water Flow Rate 100 gpm/ft2(ASTM D-4491) UV Resistance @ 500 hrs 70% retained (ASTM D-4491)

In embodiments that include a filter fabric or other separation feature,other types of fabrics (which may be comprised of cloth, plastic, nylon,or other materials) or other separation features may be used.

The thickness or height of a water retention layer may be defined as thedistance between the bottom of the water retention layer and the top ofthe water retention layer. For example, in some embodiments, the bottomof the water retention layer is that portion of the water retentionlayer in contact with an underlying roofing structure or a membrane,fabric, drain sheet, or the like interposed between the water retentionlayer and the underlying roofing structure. The top of the waterretention layer may refer generally to that portion of the waterretention layer in contact with the nutritive layer (or composite layeror what will become the nutritive layer, upon settling), it beingunderstood that “top” may not be (or may not remain) a clearly definedpoint and may refer to any point within a transition zone between thewater retention layer and the nutritive layer (or composite layer), asdiscussed above. The height of a water retention layer may vary across avegetative system of the present disclosure.

In certain preferred embodiments, the water retention layer is between 1inch and 6 inches thick (e.g., 1 inch, 2 inches, 3 inches, 4 inches, 5inches, or 6 inches). In another embodiment, the water retention layeris at least 7 inches thick, and it yet another embodiment, the waterretention layer is at least 0.5 inches thick. In one preferredembodiment, the water retention layer is between 2.5 and 3 inches thick;in another preferred embodiment, the water retention layer is between 1and 3 inches thick.

The thickness of the water retention layer may be selected based on oneor more criteria such as: (1) capacity to satisfy a targeted storm waterholding capacity, (2) weight limits of the system (e.g., based on thestructural integrity of the underlying structure), (3) upliftrequirements, (4) climate considerations, (5) moisture requirement ofthe plants of the vegetative system, and (6) total system thickness. Forexample, in an embodiment in which the water retention layer comprises 3inches of rock wool, only that water retained in the upper portion(e.g., the top 2 inches, 1.5 inches, inch, or 0.5 inch) is available toplants, e.g., via interaction with the nutritive layer. Accordingly, inthis example, the entire water retention layer serves to satisfy atargeted storm water holding capacity while only the top portion of thewater retention layer serves as a material source of water for theplants of the vegetative system. In a water retention layer comprising 3inches of rock wool with a density in the range of 8 to 16 lbs/ft³, thewater retention layer may provide adequate storm water mitigation for upto a 3.5 inch rainfall. In other embodiments, a 3 inch water retentionlayer provides adequate storm water mitigation for up to a 1.8 inchrainfall.

In certain preferred embodiments, the thickness of the water retentionlayer of a vegetative system is at least 25% of the combined thicknessof the water retention, nutritive, and weed suppression layers of thatsystem.

In some embodiments, including certain embodiments that comprise rockwool, the vertical column of the water retention layer promotesdistribution of water throughout the water retention layer and,correspondingly, discourages pooling of water at or near the top of thewater retention layer. Embodiments of the vegetative system thatdiscourage pooling of water at or near the top of the water retentionlayer provide an effective growth environment for plants of thevegetative system and mitigate the risk of root rot.

Nutritive Layer and Weed Suppression Layer

In addition to a lower water retention layer 102, vegetative systems ofthe present disclosure include a middle nutritive layer 104 and an upperweed suppression layer 106.

In certain preferred embodiments of the vegetative systems, such as theembodiment illustrated in FIG. 2, the components of the nutritive layerand weed suppression layer are applied as a composite layer 205 to awater retention layer 202 as a blend which separates into two layers;the weed suppression layer and the nutritive layer.

A composite layer 205 may separate over time (e.g., in variousembodiments, within the first growing season, within about 2 weeks,within about 1 month, within about two 2 months, or within about 3months) into two relatively distinct weed suppression and nutritivelayers. Separation may be allowed to occur naturally over time, in whichsettlement is promoted via rainfall or may be encouraged with suppliedwater application. However, there may not be clear distinction betweenthe weed suppression layer and the nutritive layer as the compositelayer (over time) may gradually transition from a coarser, drieraggregate above (e.g., the weed suppression layer) to a finer, moisteraggregate below (e.g., the nutritive layer).

In certain embodiments in which nutritive and weed suppression layersare supplied initially as a composite layer, the composite layerincludes a blend of coarse aggregate, fine aggregate, and a fine organiccomponent that will separate into an upper weed suppression layercomprising primarily of coarse aggregate and a middle nutritive layercomprising a mixture of coarse aggregate, fine aggregate, and a fineorganic component.

The composite layer 205 of such embodiments may be defined by itsparticle size distribution (PSD) ratios. The graph 300 provided in FIG.3 illustrates, for an exemplary embodiment, PSD ratios of a compositelayer. Graph 300 also provides a comparison between PSD ratios of thiscomposite layer 302 and the PSD ratios imposed under the FLL guidelines304, 306. In the embodiment illustrated on graph 300, the PSD ratios ofthe composite layer 302 contain relatively few mid-range sized particlesin comparison to the PSD ratios imposed under the FLL guidelines, whichprovides for a more uniform mix of aggregate size. Instead, the PSDratios of the exemplary composite layer include primarily coarseaggregate, some fine components (e.g., a mix of fine aggregate and fineorganic components), and relatively few mid-sized components.

In a composite layer with PSD ratios like or similar to thoseillustrated on graph 300, the fines settle into the macro-pore spacecreated by the large aggregate, leaving most of the macro-pore space inthe top portion of the profile (which becomes the weed suppressionlayer) unfilled. Because of the similarity in PSD of the fine aggregateand organics in this embodiment, the nutritive layer has a higherorganic content than the weed suppression layer and may be as high as30% by volume.

Graph 400 of FIG. 4 illustrates minimum 402 and maximum 404 PSD ratiosof certain embodiments of a composite layer. Again, FLL guidelines 406,408 are provided for reference. Table 2 below provides more detail ofthe range of PSD ratios of this embodiment.

TABLE 2 Sieve Size (in mm and the equivalent Mass Percentage of TotalU.S. Standard Mesh) Particles Passing Sieve Size 0.063 mm (#230) <=20.25 mm (#60) 1-7 1 mm (#18)  3-15 2 mm (#10)  5-20 3.35 mm (#6)  5-256.3 mm (1/4″) 45-55 9.5 mm (3/8″)  70-100 12.5 mm (1/2″) 100

In the composite layer of Table 2, very few particles (e.g., 2%, lessthan 2%, less than 1.5%, less than 0.5%, or less than 0.25%) of thecomposite layer will pass through a 0.063 mm (#230) sieve; between 1%and 7% (e.g., 1%, 2%, 3%, 4%, 5%, 6%, or 7%) of the particles (by mass)will pass through a 0.25 mm (#60) sieve; between 3% and 15% (e.g., 3%,5%, 7%_(,) 10%, 12%, or 15%) of the particles (by mass) will passthrough a 1 mm (#18) sieve; between 5% and 20% (e.g., 5%, 7%, 10%, 12%,15%, 18%, or 20%) of the particles (by mass) will pass through a 2 mm(#10) sieve; between 5% and 25% (e.g., 5%, 7%, 10%, 12%, 15%, 18%, 20%,23%, or 25%) of the particles (by mass) will pass through a 3.35 mm (#6)sieve; between 45% and 55% (e.g., 45%, 47%, 50%, 52%, or 55%) of theparticles (by mass) will pass through a 6.3 mm (¼″) sieve; between 70%and 100% (e.g., 70%, 75%, 80%, 85%, 90%, 95%, or 100%) of the particles(by mass) will pass through a 9.5 mm (⅜″) sieve; and 100% of theparticles will pass through a 12.5 mm (½″) sieve. Different PSD ratiosmay be used in other embodiments. For example, in another embodiment,some portion of the particles (e.g., 1%, 2%, 3%, 4%, or 5% by mass) willnot pass through a 12.5 mm sieve

The starting PSD ratios of a composite layer can be manipulated toachieve differing relative depths of weed suppression and nutritivelayers. For example, having established a preferred depth of weedsuppression layer and a nutritive layer of a particular vegetativesystem, as discussed in detail below, a blend may be selected for acomposite layer that will yield those approximate depths.

In one example, the composite layer is comprised of a blend of 3 partsper volume of coarse aggregate, 1 part per volume of fine aggregate, and0.75 part per volume of organic material. A 3-inch deep section of the3:1:0.75 ratio blend of this composite layer will stratify intoapproximately a 2 inch weed suppression layer and a 1 inch nutritivelayer. A deeper starting section of this blend will result in deeperweed suppression and nutritive layers of approximately the same ration,e.g., a 4-inch deep section of the 3:1:0.75 ratio blend of thiscomposite layer will stratify into approximately a 2.6 inch weedsuppression layer and a 1.3 inch nutritive layer. In some climates, thismix would be suitable for the growth of perennial succulents (such asplants in the genus Sedum).

A composite layer resulting in a thinner nutritive layer could utilize aratio of 5 parts per volume coarse aggregate, 1 part per volume fineaggregate, and 0.75 part organic content. A 3-inch deep section of the5:1:0.75 ratio blend of this composite layer will stratify intoapproximately a 2½ inch weed suppression layer and a ½ inch nutritivelayer.

The combined PSD ratios of a vegetative system in which nutritive layersand weed suppression layers are applied separately, rather than as acomposite layer, may exhibit characteristics similar to or the same asthose illustrated in Table 2 and Graph 400. In an alternative embodimentof a vegetative system, in which the fine aggregate and fine organicparticles of the nutritive layer are applied on top of course aggregate,the combined PSD ratios of the nutritive and weed suppression layers ofthat embodiment exhibit PSD ratios as illustrated in Table 3. Inparticular example of this embodiment, between 10% and 30% of the totalcombined mass of the nutritive and weed suppression layers consists of acombination of fine aggregate and fine organic particles that will passthrough a 12.5 mm (½″) sieve but be retained by a 9.5 mm (⅜″) sieve.

TABLE 3 Combined Nutritive and Weed Suppression Layers Sieve Size (in mmand the equivalent Mass Percentage of Total U.S. Standard Mesh)Particles Passing Sieve Size 0.01 mm (pan) <=1 0.063 mm (#230) <=1 0.25mm (#60) 1-2 1 mm (#18) 1-3 2 mm (#10) 2-4 3.35 mm (#6) 3-6 6.3 mm(1/4″)  4-10 9.5 mm (3/8″)  5-20 12.5 mm (1/2″)  7-100 25.4 mm (1″) 15-100 38.1 mm (1.5″)  30-100 50.8 mm (2″)  50-100 63.5 mm (2.5″) 100%

In the combined nutritive and weed suppression layers of Table 3, veryfew particles (e.g., 1%, less than 1%, less than 0.5%, or less than0.25%) of the nutritive layer will pass through a 0.01 mm (pan) sieve ora 0.063 mm (#230) sieve; between 1% and 2% (e.g., 1%, 1.5%, or 2%) ofthe particles (by mass) will pass through a 0.25 mm (#60) sieve; between1% and 3% (e.g., 1%, 1.5%, 2%, 2.5%, or 3%) of the particles (by mass)will pass through a 1 mm (#18) sieve; between 2% and 4% (e.g., 2%, 2.5%,33%, 3.5%, or 4%) of the particles (by mass) will pass through a 2 mm(#10) sieve; between 3% and 6% (e.g., 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, or6%) of the particles (by mass) will pass through a 3.35 mm (#6) sieve;between 4% and 10% (e.g., 4%, 6%, 8%, or 10%) of the particles (by mass)will pass through a 6.3 mm (¼″) sieve; between 5% and 20% (e.g., 5%,10%, 15%, or 20%) of the particles (by mass) will pass through a 9.5 mm(⅜″) sieve; between 7% and 100% (e.g., 7%, 10%, 20%, 30%, 40%, 50%, 60%,70%, 80%, 90%, or 100%) of the particles (by mass) will pass through a12.5 mm (½″) sieve; between 15% and 100% (e.g., 15%, 20%, 30%, 40%, 50%,60%, 70%, 80%, 90%, or 100%) of the particles (by mass) will passthrough a 25.4 mm (1″) sieve; between 30% and 100% (e.g., 30%, 40%, 50%,60%, 70%, 80%, 90%, or 100%) of the particles (by mass) will passthrough a 38.1 mm (1.5″) sieve; between 50% and 100% (e.g., 50%, 60%,70%, 80%, 90%, or 100%) of the particles (by mass) will pass through a50.8 mm (2″) sieve; and 100% of the particles will pass through a 63.5mm (2.5″) sieve. In another embodiment, some portion of the particles(e.g., 1%, 2%, 3%, 4%, or 5%, by mass) will not pass through a 63.5 mmsieve.

Graph 500 of FIG. 5 provides an alternative illustration of minimum 502and minimum 504 PSD ratios of combined nutritive and weed suppressionlayers of an embodiment of a vegetative system. FLL guidelines 506, 508are provided for reference.

Table 4 below, illustrates the range of PSD ratios of the nutritivelayer that may result following stratification of the composite layer ofTable 2. Similarly, a nutritive layer applied separately onto a watersuppression layer may include a mixture of fine aggregate particles andfine organic particles with PSD ratios shown on Table 4. A nutritivelayer may comprise a mixture of fine aggregate particles and fineorganic particles of that, in combination, exhibit these PDS ratios;preferably a nutritive layer comprises a mixture of fine aggregateparticles and fine organic particles both of which separately exhibitthese PSD ratios.

TABLE 4 Nutritive Layer Sieve Size (in mm and the equivalent MassPercentage of Total U.S. Standard Mesh) Particles Passing Sieve Size0.063 mm (#230) <=2 0.25 mm (#60) 1-10 1 mm (#18)  2 to 10 2 mm (#10) 10to 40 3.35 mm (#6) 20 to 50 6.3 mm (1/4″) 40-60 9.5 mm (3/8″)  70-10012.5 mm (1/2″) 100

In the nutritive layer of Table 4, very few particles (e.g., less than2%, less than 1.5%, less than 0.5%, or less than 0.25%) of the nutritivelayer will pass through a 0.063 mm (#230) sieve; between 1% and 10%(e.g., 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%) of the particles (bymass) will pass through a 0.25 mm (#60) sieve; between 2% and 10% (e.g.,2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%) of the particles (by mass) willpass through a 1 mm (#18) sieve; between 10% and 40% (e.g., 10%, 13%,17%, 23%, 20%, 23%, 25%, 27%, 30%, 33%, 35%, 37%, or 40%) of theparticles (by mass) will pass through a 2 mm (#10) sieve; between 20%and 50% (e.g., 20%, 23%, 25%, 27%, 30%, 33%, 35%, 37%, 40%, 43%, 45%,47%, or 50%) of the particles (by mass) will pass through a 3.35 mm (#6)sieve; between 40% and 60% (e.g., 40%, 43%, 45%, 46%, 50%, 53%, 55%,57%, or 60%) of the particles (by mass) will pass through a 6.3 mm (¼″)sieve; between 70% and 100% (e.g., 70%, 75%, 80%, 85%, 90%, 95%, or100%) of the particles (by mass) will pass through a 9.5 mm (⅜″) sieve;and 100% of the particles will pass through a 12.5 mm (½″) sieve.Different PSD ratios may be used in other embodiments. For example, inanother embodiment, some portion of the particles (e.g., 1%, 2%, 3%, 4%,or 5%, by mass) will not pass through a 12.5 mm sieve.

Graph 600 of FIG. 6 provides an alternative illustration of the minimum602 and maximum 604 PSD ratios of certain embodiments of a nutritivelayer of a vegetative system. Again, the range of PSD ratios for theseembodiments are compared to those of the FLL guidelines 606, 608.

Table 5 below, illustrates a range of PSD ratios of the mixture of fineaggregate particles and fine organic particles that may be applied tothe top of coarse aggregate (e.g., coarse aggregate with a PSD ratio inthe range illustrated on Table 7 below) to result, upon settling, in amiddle nutritive layer comprising this mixture of materials incombination with the coarse aggregate particles. (In another embodiment,a separately applied nutritive layer comprising a mixture of fineaggregate particles and fine organic particles exhibits PSD ratios inthe range shown on Table 4.) Graph 700 of FIG. 7 provides an alternativeillustration of these minimum 702 and maximum 704 PSD ratios. Thematerials of Table 5 may comprise a mixture of fine aggregate particlesand fine organic particles of that, in combination, exhibit these PDSratios; preferably, the materials comprise a mixture of fine aggregateparticles and fine organic particles both of which separately exhibitthese PSD ratios.

TABLE 5 Nutritive Layer Fine Particle Components Sieve Size (in mm andthe Mass Percentage of Total equivalent U.S. Standard Mesh) ParticlesPassing Sieve Size 0.01 mm (pan) <=2 0.063 mm (#230) <=2 0.25 mm (#60) 2 to 15 1 mm (#18)  5 to 30 2 mm (#10) 10 to 50 3.35 mm (#6) 20 to 706.3 mm (1/4″) 40-90 9.5 mm (3/8″) 100

Most of the particles in a nutritive layer of this embodiment arebetween 2 mm and 6.3 mm in size. More specifically, in the nutritivelayer of Table 5, very few particles (e.g., less than 2%, less than1.5%, less than 0.5%, or less than 0.25%) of the nutritive layer willpass through a 0.01 mm (pan) sieve or a 0.063 (#230) sieve; between 2%and 15% (e.g., 2%, 4%, 6%, 8%, 10%, 12%, 14%, or 15%) of the particles(by mass) will pass through a 0.25 mm (#60) sieve; between 5% and 30%(e.g., 5%, 10%, 20%, 25%, or 30%) of the particles (by mass) will passthrough a 1 mm (#18) sieve; between 10% and 50% (e.g., 10%, 13%, 17%,23%, 20%, 23%, 25%, 27%, 30%, 33%, 35%, 37%, 40%, 43%, 45%, 47%, or 50%)of the particles (by mass) will pass through a 2 mm (#10) sieve; between20% and 70% (e.g., 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or70%) of the particles (by mass) will pass through a 3.35 mm (#6) sieve;between 40% and 90% (e.g., 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%,85%, or 90%) of the particles (by mass) will pass through a 6.3 mm (¼″)sieve; and 100% of the particles will pass through a 9.5 mm (⅜″) sieve.Different PSD ratios may be used in other embodiments. For example, inanother embodiment, some portion of the particles (e.g., 1%, 2%, 3%, 4%,or 5%, by mass) will not pass through a 9.5 mm sieve.

In preferred embodiments of vegetative systems of this disclosure, thenutritive layer is the primary rooting zone, is composed of a range ofaggregate sizes and organic matter, and is positioned in the moist spacebetween a dry, upper weed suppression layer and a lower water retentionlayer. In certain preferred embodiments, between 60% and 40% of thenutritive zone is comprised of particles that will pass through a 6.3 mmsieve but will be retained by a 2 mm sieve. In other embodiments between10% and 60%, between 20% and 60%, between 30% and 60%, between 45% and55%, between 47% and 53%, or approximately 50% of the nutritive zone iscomprised of particles that will pass through a 6.3 mm sieve but beretained by a 2 mm sieve. The PSD ratios of these embodiments may createa high percentage of micropore space.

The thickness or height of a nutritive layer may be defined as thedistance between the bottom of the nutritive layer and the top of thenutritive layer. For example, in some embodiments, the bottom of thenutritive layer is that portion of the nutritive layer in contact withthe water retention layer, e.g., in some embodiments of a waterretention layer, a filter fabric comprising a water retention layer. Thetop of the nutritive layer may refer generally to any point within atransition zone between the nutritive layer and the weed suppressionlayer, as discussed above. In an embodiment in which a filter fabric,membrane, or other material is interposed between the nutritive layerand the weed suppression layer, the top of the nutritive layer may referto that portion of the nutritive layer in contact with such filterfabric, membrane, or other material. The height of a nutritive layer mayvary across a vegetative system of the present disclosure.

In some embodiments, the nutritive layer is between 0.25 and 18 inchesthick (e.g., 0.25 inch, 0.5 inch, 1 inch, 4 inches, 6 inches, 8 inches,10 inches, 12 inches, 15 inches, or 18 inches). In certain preferredembodiments, the nutritive layer is between 0.25 and 3 inches thick(e.g., 0.25 inch, 0.5 inch, 1 inch, 1.5 inches, 2 inches, 2.5 inches, or3 inches). The thickness of the nutritive layer may be selected, atleast in part, based on the habitable root zone of the vegetationselected for the vegetative system. In an embodiment in which thenutritive layer is between 1 and 4 inches thick, the vegetation of thevegetative system may include sedum. In an embodiment in which thenutritive layer is between 8 and 12 inches thick, the vegetation of thevegetative system may include shrubs, and in an embodiment in which thenutritive layer is 18 inches thick, the vegetation of the vegetativesystem may include small trees.

A nutritive layer may be further defined by its water retentioncapacity. In some embodiments of a nutritive layer, the nutritive layerretains less than 25% of its weight in water. In other embodiments, thenutritive layer retains between 25% and 15% (e.g., 25%, 22%, 20%, 17%,or 15%) of its weight in water.

Table 6 below illustrates the range of PSD ratios of the weedsuppression layer that may result following stratification of thecomposite layer of Table 2.

TABLE 6 Weed Suppression Layer Mass Percentage of Total Particles SieveSize (metric and imperial) Passing Sieve Size 0.063 mm (#230 sieve) <20.25 mm (#60 sieve) <2 1 mm (#18 sieve) <2 2 mm (#10 sieve) <2 3.35 mm(#6 sieve) <2 6.3 mm (1/4″) 15-50 9.5 mm (3/8″)  70-100 12.5 mm (1/2″):100

In the embodiment illustrated, the weed suppression layer is comprisedmostly of ¼ inch to ½ inch (6.3 mm to 12.5 mm) particles; specifically,particles that will pass through a ½ inch sieve but that will not passthrough a #6 sieve. In various example embodiments, less than 10%, lessthan 8%, less than 6%, less than 4%, less than 4%, less than 1%, lessthan 0.5%, or less than 0.25% of the weed suppression layer will passthrough a 3.35 mm (#6) sieve; between 15% and 50% (e.g., 15%, 20%, 25%,30%, 35%, 40%, 45%, or 50%) of the particles (by mass) will pass througha 6.3 mm (¼″) sieve; between 70% and 100% (e.g., 70%, 75%, 80%, 85%,90%, 95%, or 100%) of the particles (by mass) will pass through a 9.5 mm(⅜″) sieve; and 100% of the particles will pass through a 12.5 mm (½″)sieve. Different PSD ratios may be used in other embodiments. Forexample, in another embodiment, some portion of the particles (e.g., 1%,2%, 3%, 4%, or 5%, by mass) will not pass through a 12.5 mm sieve.

Graph 800 of FIG. 8 provides an alternative illustration of the minimum802 and maximum 804 PSD ratios of certain embodiments of a weedsuppression layer of a vegetative system. Again, the range of PSD ratiosfor these embodiments are compared to those of the FLL guidelines 806,808.

Table 7 illustrates the PSD range of another embodiment of a weedsuppression layer. Graph 900 of FIG. 9 provides an alternativeillustration of the minimum 902 and maximum 904 PSD ratios of certainembodiments of a weed suppression layer of a vegetative system, incomparison to the PSD ratios for these embodiments are compared to thoseof the FLL guidelines 906, 908.

TABLE 7 Weed Suppression Layer Mass Percentage of Total Particles SieveSize (metric and imperial) Passing Sieve Size 63.5 mm (2.5″) 100% 50.8mm (2″) 30-100 38.1 mm (1.5″) 10-100 25.4 mm (1″)  5-100 12.5 mm (0.5″) 5-100

In the embodiment illustrated, the weed suppression layer is comprisedmostly of coarse, inorganic aggregate particles that are between ½ inchand 2.5 inches; specifically, particles that will pass through a 2.5inch sieve but that will not pass through a 1.2 inch sieve. In apreferred embodiment of this example, all (or substantially all) of theparticles will be retained by a 9.5 mm (⅜″) sieve. In various exampleembodiments, between 5% and 100% (e.g., 5%, 10%, 20%, 30%, 40%, 50%,60%, 70%, 80%, 90%, or 100%) of the particles (by mass) will passthrough a 12.5 mm (½″) sieve; between 5% and 100% (e.g., 5%, 10%, 20%,30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%) of the particles (by mass)will pass through a 25.4 mm (1″) sieve; between 10% and 100% (e.g., 10%,20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%) of the particles (bymass) will pass through a 38.1 mm (1.5″) sieve; between 30% and 100%(e.g., 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%) of the particles (bymass) will pass through a 50.8 mm (2″) sieve; and 100% of the particleswill pass through a 63.5 mm (2.5″) sieve. In another embodiment, someportion of the particles (e.g., 1%, 2%, 3%, 4%, or 5%, by mass) will notpass through a 63.5 mm sieve.

A weed suppression layer with a PSD of or similar to a PSD in the rangeillustrated in Table 6 and graph 800, or in the range illustrated inTable 7 and graph 900, creates a dry zone that is hostile to weed seeds,but hospitable to plants of the genus Sedum. In this embodiment, only asmall portion of the weed suppression layer of this embodiment comprisesorganic matter.

The thickness or height of a weed suppression layer may be defined asthe distance between the bottom of the weed suppression layer and thetop of the weed suppression layer. For example, in some embodiments, thebottom of the weed suppression layer may refer generally to any pointwithin a transition zone between the nutritive layer and the weedsuppression layer, as discussed above. In an embodiment in which afilter fabric, membrane, or other material is interposed between thenutritive layer and the weed suppression layer, the bottom of the weedsuppression layer may refer to that portion of the weed suppressionlayer in contact with such filter fabric, membrane, or other material.In many embodiments, the top of the weed suppression layer will be thetop of the vegetative system; however, vegetation planted in thevegetative system will be above the top of the weed suppression layerand, in some embodiments, a vegetation mat, a filter fabric, membrane,or other material may be placed on top of the weed suppression layer ofa vegetative system of the present disclosure. The height of a weedsuppression layer may vary across a vegetative system of the presentdisclosure.

In certain preferred embodiments, the weed suppression layer is between0.5 and 2 inches thick (e.g., 0.5 inch, 1 inch, 1.5 inches, or 2 inches)and minimizes light penetration through to the nutritive layer. In otherembodiments, the weed suppression layer is between 1 and 4 inches think(e.g., 1 inch, 1.5 inches, 2 inches, 2.5 inches, 3 inches, 3.5 inches,or 4 inches). In another embodiment, the weed suppression layer is 0.25inch thick.

In preferred embodiments, the capillary action of weed suppression andnutritive layers with PSDs in the ranges listed on Table 4 and Table 6allows water to flow through to the water retention layer with littleretention of water within the weed suppression layer and minimalretention of water within the nutritive layer. Accordingly, in theseembodiments, the nutritive layer remains moist, via its own minimalwater retention and interaction with the water retention layer, but isunlikely to become saturated at a level that will promote root rot orotherwise be detrimental to the health of plants of the vegetativesystem.

When considering embodiments of vegetative systems in which thenutritive and weed suppression layers are provided separately, the PSDratios of the layers as initially applied may be the same as or similarto the PSD ratios of the nutritive and weed suppression layers thatresult from separation of an initial composite layer.

In other embodiments, such as the embodiment of a vegetative system 1000illustrated in FIG. 10, when a nutritive layer 1004 is applied to awater retention layer 1002 as a separate layer, relatively few particles(e.g., less than 20%, less than 15%, less than 10%, less than 7%, lessthan 5%, less than 3%, or less than 1%, by mass) that will not passthrough a 6.3 mm (1.4″) sieve are included in the nutritive layer 1004.In vegetative system 1000, most (e.g., at least 70%, at least 73%, atleast 75%, at least 77%, at least 80%, at least 83%, at least 85%, atleast 87%, at least 90%, at least 93%, or at least 95%) of the particlesof the weed suppression layer 706 will pass through a ½ (12.5 mm) sievebut will not pass through a 3.35 mm (#6) sieve.

The coarse aggregate of the nutritive layer (for embodiments thatinclude coarse aggregate in the nutritive layer), the weed suppressionlayer, and, if applicable, the composite layer, generally refers tothose particles that will not pass through a 3.35 mm (#6) sieve;however, other appropriate characteristics may be used to define anaggregate as “coarse”. Inorganic materials consisting primarily ofminerals are preferred for the coarse aggregate of vegetative systems ofthe invention. Materials selected for the coarse aggregate preferablyresist fracturing and decay and, therefore, substantially retain thestarting PSDs. Such materials may include one or more of crushed brick,granite, bottom ash, haydite, diatomite, calcined clays, limestone,silicaceous gravel, flint, marble, naturally occurring volcanicaggregate, and other materials with similar durability.

In some preferred embodiments, the coarse aggregate consists primarilyof crushed brick. Particularly preferred is post-industrial waste brickor demolition product brick.

Preferably, at least 80% of the weed suppression layer (by mass) iscomposed of inorganic material. In other embodiments, at least 90%, atleast 95%, at least 98%, or at least 99% of the weed suppression layer(by mass) is composed of inorganic material.

Fine aggregate particles generally refers to particles that will passthrough a 3.35 mm (#6) sieve; however, other appropriate characteristicsmay be used to define a particle as “fine.”

In certain preferred embodiments, the fine aggregate of the nutritivelayer or the composite layer (which may be present in relatively smallquantities in the weed suppression layer) has a cation exchange capacity(CEC) in the range of 6 cmol/kg¹ to 10 cmol/kg¹ (e.g., 6 cmol/kg¹, 6.5cmol/kg¹, 7 cmol/kg¹, 7.5 cmol/kg¹, 8 cmol/kg¹, 8.5 cmol/kg¹, 9cmol/kg¹, 9.5 cmol/kg¹, 9.9 cmol/kg¹, or 10 cmol/kg¹). A CEC in thisrange, in combination with moisture, provides a high level of nutrientavailability within the nutritive layer. In some embodiments, the CEC ofthe fine aggregate is greater than 10 cmol/kg¹, and in otherembodiments, the CEC of the fine aggregate is less than 6 cmol/kg¹.

In certain preferred embodiments, the fine aggregate particles of thevegetative system resist fracturing or decay and, therefore,substantially retain the starting PSD. Inorganic materials consistingprimarily of minerals are preferred for the fine aggregate of vegetativesystems of the invention. Such materials may include one or more ofcrushed brick, pumice, calcined clay, haydite, appropriate volcanic rock(scoria), diatomite, zeolite, akadama, kanuma, high density crushedfoamed glass, granite, and other materials with similar durability andinternal microporsity. In a preferred embodiment of a vegetative systemof this disclosure, the fine aggregate particles consists primarily ofcrushed brick.

Materials for each of the coarse aggregate and the fine aggregate may befurther defined by their internal micropore and mesoporecharacteristics. Materials with a relatively high internal micropore andmesopore space or certain inherent arrangements of micropores andmacropores will promote water transmission to the surface of thevegetative system profile; such water transmission partially dictatesrates of evaporative loss and evaporative cooling. In some embodiments,material that includes internal micropores is preferred for the coarseaggregate, the fine aggregate, or both.

In certain preferred embodiments of vegetative systems of the invention,the density of the aggregate media is between 40 and 80 lbs/ft³ (e.g.,40 lbs/ft³, 45 lbs/ft³, 50 lbs/ft³, 55 lbs/ft³, 60 lbs/ft³, 65 lbs/ft³,70 lbs/ft³, 75 lbs/ft³, or 80 lbs/ft³). In a particularly preferredembodiment, the density of the aggregate is approximately 55 lbs/ft³.

In some embodiments, organic matter comprises between 10% and 50% (e.g.,10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%) of the nutritive layer,by mass. In other embodiments, organic matter comprises more than 50% ofthe nutritive layer. In yet another embodiment, organic matter comprisesless than 10% of the nutritive layer.

For applications that must be compliant with fire regulatory codes, atotal organic content of the combined weed suppression layer andnutritive layer preferably comprises no more than 20% of total aggregatevolume.

Broadly speaking the organic matter of the nutritive layer or thecomposite layer (which may be retained or otherwise found in the weedsuppression layer to a small extent) provides a nutrient source forplants in the vegetative system. Over time, the original organicmaterial may be replaced and replenished with organic matter via shedleaves and decayed root fibers.

Organic material of the nutritive layer may include one or more of pinebark fines, a peat based organic source, aged compost, coir dust, milledlong fiber sphagnum moss, grade 1 biosolids, or other organic materials.In certain preferred embodiments, the organic material consistsprimarily of aged pine bark fines.

In certain preferred embodiments, the organic matter substantiallyretains its structural integrity for a long time (e.g., at least 5years, at least 10 years, or more than 10 years) and has a cationexchange capacity (CEC) in the range of 6 cmol/kg¹ to 10 cmol/kg¹ (e.g.,6 cmol/kg¹, 6.5 cmol/kg¹, 7 cmol/kg¹, 7.5 cmol/kg¹, 8 cmol/kg¹, 8.5cmol/kg¹, 9 cmol/kg¹, 9.5 cmol/kg¹, 9.9 cmol/kg¹, or 10 cmol/kg¹).

In addition, the organic component may include micro and macronutrients, e.g., micro and macro nutrients that are largely waterinsoluble and that are necessary or desirable for long term healthyplant growth. In these and other embodiments, nutrients may be appliedafter a vegetative system has been assembled, e.g., instead of or inaddition to inclusion of nutrients in the organic component of thenutritive layer.

The weed suppression layers and nutritive layers may be further definedby the water retention capacity of the layers, both individually and incombination. In some embodiments, the aggregate component (top andmiddle layers combined) holds approximately 0.15 gallons per 1 inchdepth, most of which is retained within the nutritive layer. In oneexample embodiment, the water retention capacity, by volume, of thecombined weed suppression and nutritive layers (or of the compositelayer), is approximately 26%, calculated as follows:

A 12-inch by 12-inch sample of a 1-inch thick combined weed suppressionand nutritive layer (or of the composite layer), e.g., a sample with avolume of 0.623 gallons, weighs 4.52 pounds when dry and 5.83 poundswhen saturated (according to the steps described above). That sample isretaining 1.31 pounds of water (5.83−4.52=1.31).

1 gallon of water typically weighs 8.35 pounds. Using this weight, 1.31pounds of retained water is approximately equivalent to 0.16 gallons ofretained water (1.31/8.35=0.16).

In this example, 0.16 gallons of retained water equates to a waterretention of 26% of its dry volume (0.16/0.623=0.26).

In certain embodiments, the water retention capacity, by volume, of thecombined weed suppression and nutritive layer (or of the compositelayer) is between 60% and 20% (e.g., 60%, 55%, 50%, 45%, 40%, 35%, 30%,25%, or 20%).

Other Components of Vegetative Systems

Vegetation

Certain preferred embodiments of vegetative systems of this disclosureare particularly suited for plants in the genus Sedum and related roofplants. Among such plants are Allium cernuum, Allium schoenoprasum,Allium senescens montanum, Delosperma cooperi, Delosperma nubigenum,Dianthus carthusianorum, Sedum acre, Sedum aizoon, Sedum ellacombianum,Sedum floriferum, Sedum hybridum, Sedum kamtschaticu, Sedum oreganum,Sedum pulchellum, Sedum seiboldii, Sedum rupestre, Sedum spurium, Sedumstoloniferum, Sedum telephium, Phedimus takesimense, and Talinumcalycinum. Other embodiments of vegetative systems of this disclosuremay be suitable for ornamental grasses, shrubs, small trees, and otherperennials, annuals, biennials, or other vegetation.

Filter Fabric

In addition to the filter fabric that may be a component of the waterretention layer, in certain embodiments, vegetative systems may includea filter or separate fabric, such as a filter fabric withcharacteristics similar to those listed in Table 1 above, between otherlayers or components.

Membrane Protection Layers

The water retention layer of vegetative systems of the presentdisclosure may be placed directly on a waterproofing membrane of atypical roofing construction. However, if required by the roofingmanufacture, or if otherwise necessary or desirable, the water retentionlayer may be placed on top of a combination of membrane protectionlayers. Such layers may include one or more of an air layer, aprotection layer, and a root barrier.

An air layer refers to an impervious layer of material that is held offthe roofing membrane to create an air space between the water retentionlayer of a vegetative system and the roof, in a manner that minimizesair contact with the water retention layer, thereby reducing thelikelihood that the water retention layer will become excessively dry.In some embodiments, a non-perforated, cup-type composite drain sheet isused to create an air layer. Such a drain sheet may be approximately 40inches thick, may have a flow at a hydraulic gradient of 1 of 21g/min/ft (as measured per ASTM D-4716), and a compressive strength of15,000 psf (as measured per ASTM D-1621).

A protection layer refers to a material used to protect thewaterproofing membrane from mechanical damage during and afterinstallation. By way of example, a needle punched nonwoven polypropylenefiber geotextile may be used as a protection layer.

A root barrier refers to a root-impervious liner placed just above thewaterproofing membrane and, preferably, exhibits characteristics (suchas tensile strength, elongation, tear resistance, puncture resistance,UV resistance) suitable for such purpose.

Other items that may be used in combination with vegetative systems ofthe present disclosure include a temporary surface protection layer(e.g., a biodegradable fabric), edging (e.g., aluminum L-shaped edging),stepping stone pavers, or gravel borders.

Assembling Vegetative Systems

Discussed above are factors that may be considered in selectingquantities of and materials for the components of the water retention,nutritive, and weed suppression layers. In addition, quantities of andmaterials for the components of vegetative systems may be selected basedon factors applicable to the system as a whole, such as upliftresistance, weight, storm water retention needs, and otherclimate-specific factors.

The density of the coarse aggregate of the weed suppression andnutritive layers will largely dictate the minimum aggregate depth toachieve a desired uplift resistance because that material provides thebulk of the unsaturated weight of the system. In an example embodiment,a system comprising weed suppression and nutritive layers with acombined depth of 2.25 inches and a 1 inch water retention layer willhave a dry weight of 11 lb/ft² and, accordingly is sufficiently heavy toachieve a #4 ballast rating (based on ANSI/SPRI RP-14 Class).

The capacity of the roof (or other supporting structure) may dictateover-all weight restrictions. Accordingly, in such instances the weightof the entire system, both dry and fully saturated, should beconsidered.

Although the water retention layer provides the bulk of storm waterretention, some water retention is provided by the nutritive layer (anda small portion by the weed suppression layer). For example, in certainpreferred embodiments, the combined nutritive and weed suppressionlayers will retain approximately 0.15 gallons of water per square footper inch of depth, which equates to a rain capacity of about 0.25inches. Accordingly, when determining minimum requirements for avegetative system of the present disclosure that will provide adequatestorm water protection for a particularly sized rain event, the waterretention capacity of the entire system may be considered.

Fire resistance will be determined based on the entire system and,accordingly achieving a particular fire resistance rating will bedependent upon the combination of materials, and quantities ofmaterials, selected for the system components.

Table 8 below, lists the weight, water holding capacity, maximum rainevent capacity, and other features of various combinations of sizes ofwater retention layers and weed suppression and nutritive layers(referred to collectively in Table 5 as the “media layer”). In each ofthese embodiments, the water retention layer consists primarily of rockwool with a density of 8 lbs/ft³, the nutritive layer consists primarilyof a mix of crushed brick coarse and fine aggregate and organic fineswith a PSD ratio similar to the range shown in Table 4, and the weedsuppression layer consists primary of crushed brick coarse aggregatewith a PSD ratio similar to the range shown in Table 6.

TABLE 8 Media Maximum Total Layer/Water Maximum Water Rain SystemRetention Dry Fully Retention Event Depth Layer Weight SaturatedCapacity Capacity ANSI (in Depths (in Weight (in (in ANSI/SPRI VF-1inches) (in inches) lb/ft²) (in lb/ft²) gal/ft²) inches) RP-14 ClassRating 2 1/1 5-6 11-12 0.7 1.1 N/A Class A 3.25 2.25/1   11 18-19 0.91.4 #4 ballast Class A 4 3/1 13-15 22-24 1.0 1.5 #2 ballast Class A 31/2 6-7 16-17 1.2 2.0 N/A Class A 4.25 2.25/2   11-12 23-24 1.5 2.2 #4ballast Class A 5 3/2 15-16 28-29 1.6 2.4 #2 ballast Class A 6 3/3 15-1633-34 2.1 3.4 #2 ballast Class A

In these examples, retention performances listed were gathered viaempirical measurements. The ANSI/SPRI RP-14 system classification listedfor each profile reflects the wind uplift resistance classification foreach system. The ANSI VF-1 Rating is indicative of fire resistance.

FIG. 2 illustrates an exemplary embodiment of a newly-assembledvegetative system of the invention comprising a composite layer 205. Thesystem 200 of FIG. 2 may be assembled by installing the water retentionlayer 202 over the membrane protection layers 208 that have been placedon top of the roof system 210. The water retention layer 202 may beinstalled with hand-tight joints or other appropriate installationmethods. In this embodiment, the water protection layer 202 comprises afilter fabric 212. Media comprising a composite layer 205 may beinstalled over the water protection layer 202 to the desired depth.

Vegetation may be installed in the composite layer 205 in accordancewith accepted horticulture practice. Nutrients, such as phosphorus,nitrogen, calcium, magnesium, chlorine, iron, boron, and zinc may beapplied to the surface of the vegetative system, e.g., in a slow releaseformulation. In an example embodiment, 50 lbs/15,000 f² of a 18-1-8+Fe(which signifies the nitrogen, phosphorus, potassium ratio plus chelatediron) mixture, formulated to be 80% slow release and 20% quick release,is applied upon assembly of the vegetative system.

Over time, the system 200 of FIG. 2 will begin to resemble the system100 of FIG. 1 with a more distinct nutritive layer 104 and weedsuppression layer 106; vegetation 108 may become established within thevegetative system.

In another embodiment, a vegetative system may be assembled byinstalling the water retention layer over membrane protection layersthat have been placed on top of the roof system. Media comprising anutritive layer may be installed over the water protection layer to thedesired depth and then media comprising a weed suppression layer may beinstalled over the nutritive layer to the desired depth.

Vegetation may be installed in the vegetative system in accordance withaccepted horticulture practice and nutrients may be applied to thesurface of the vegetative system.

In another embodiment of methods of installing a vegetative system, onethat is particularly preferred for use in connection with a vegetativesystem comprising a weed suppression layer with a PSD in the rangeillustrated in Table 7 and a mixture of fine aggregate and fine organicparticles with a PSD in the range illustrated in Table 5, a waterretention layer is installed as described above and then the coarseaggregate that comprises the weed suppression layer is installed on thewater retention layer to the desired depth. The blend of fine aggregateand fine organic particles that comprise the nutritive layer is theninstalled on top of the coarse aggregate.

Over time (e.g., in various embodiments, within the first growingseason, within about 2 weeks, within about 1 month, within about two 2months, or within about 3 months) the materials will separate to form asubstantially distinct lower nutritive layer and an upper weedsuppression layer. Separation may be allowed to occur naturally overtime, in which settlement is promoted via rainfall or may be encouragedwith supplied water application. However, there may not be cleardistinction between the weed suppression layer and the nutritive layeras the composite layer (over time) may gradually transition from acoarser, drier aggregate above (e.g., the weed suppression layer) to afiner, moister aggregate below (e.g., the nutritive layer).

A vegetative system is preferably disposed on the roof of a structure.In an embodiment, the vegetative system covers at least 100 square feetof the roof. In another embodiment, the vegetative system covers atleast 250 square feet of the roof, and in a further embodiment, thevegetative system covers at least 500 square feet of the roof. Coverageneed not be contiguous and portions of a vegetative system disposed on aroof may be separated by walkways or other gaps.

Various characteristics of vegetative systems of the invention representsignificant improvements over existing vegetative systems. For example,by deviating from particle size distributions recommended by the FFLguidelines, certain vegetative systems of the invention promote waterflow through to the water retention layer and facilitate a level ofmoisture within the nutritive layer that is beneficial to healthy plantgrowth. Furthermore, by providing (in certain preferred embodiments)substantially distinct zones (or layers) to serve as the primary sourceof the functions of water retention, nutritive source, and weedsuppression, the functionality of each distinct zone may be maximized,thereby improving the functionality of the system as a whole.

In addition, vegetative systems of the invention may retain more stormwater than traditional green roofs. Measuring storm water performanceempirically indicates that a 2 inch thick vegetative system of theinvention will provide storm water retention comparable to a traditional4-inch green roof. Similarly, such measurements indicate a 4 inch thickvegetative system of the invention will retain as much storm water as an8-inch thick traditional green roof.

Without departing from the spirit and scope of this invention, one ofordinary skill can make various changes and modifications to theinvention to adapt it to various usages and conditions. As such, thesechanges and modifications are properly, equitably, and intended to be,within the full range of equivalence of the following claims.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present invention andwithout diminishing its intended advantages. It is therefore intendedthat such changes and modifications be covered by the appended claims.

What is claimed is:
 1. A vegetative system disposed on a roof of astructure, the vegetative system comprising: an upper weed suppressionlayer; a middle nutritive layer; and a lower water retention layer;wherein: the water retention layer has a water retention capacity, byvolume, of at least approximately 60%; the nutritive layer comprises amixture of fine aggregate particles and fine organic particles that willpass through a 3.35 mm sieve; and the weed suppression layer comprisescoarse aggregate particles that will not pass through a 3.35 mm sieve.2. The vegetative system of claim 1 in which the water retention layerhas a water retention capacity, by volume, of at least approximately 80%and the nutritive layer has a water retention capacity, by volume, ofless than approximately 60%.
 3. The vegetative system of claim 2 inwhich the water retention layer retains at least approximately 80% ofits water retention capacity under 100 pounds of compression.
 4. Thevegetative system of claim 3 in which the water retention layercomprises rock wool.
 5. The vegetative system of claim 4 in which thedensity of the rock wool is in the range of approximately 8 pounds percubic foot to approximately 16 pounds per cubic foot.
 6. The vegetativesystem of claim 5 in which the height of the water retention layer isbetween approximately 1 inch and approximately 6 inches.
 7. Thevegetative system of claim 1 in which the nutritive layer furthercomprises coarse aggregate particles that will not pass through a 3.35mm sieve.
 8. The vegetative system of claim 7 in which (a) betweenapproximately 10% and approximately 40% of the particles (by mass)comprising the nutritive layer will pass through a 2 mm sieve; betweenapproximately 20% and approximately 50% of the particles (by mass)comprising the nutritive layer will pass through a 3.35 mm sieve;between approximately 40% and approximately 60% of the particles (bymass) comprising the nutritive layer will pass through a 6.3 mm sieve;and at least approximately 70% of the particles (by mass) comprising thenutritive layer will pass through a 9.5 mm sieve; and (b) less than 10%of the particles (by mass) comprising the weed suppression layer willpass through a 3.35 mm sieve; between 15% and 50% of the particles (bymass) comprising the weed suppression layer will pass through a 6.3 mmsieve; and at least approximately 70% of the particles (by mass)comprising the weed suppression layer will pass through a 9.5 mm sieve.9. The vegetative system of claim 8 in which the organic matterparticles of the nutritive layer comprise between approximately 20% andapproximately 30% of the mass of the nutritive layer.
 10. The vegetativesystem of claim 8 in which the organic matter particles of the nutritivelayer comprise pine fines and in which the fine aggregate particles andthe coarse aggregate particles of the nutritive layer comprise crushedbrick.
 11. The vegetative system of claim 8 in which the fine aggregateparticles and the coarse aggregate particles of the nutritive layerconsist primarily of crushed brick.
 12. The vegetative system of claim 1in which the nutritive layer comprises particles having a cationexchange capacity (CEC) in the range of approximately 6 cmol/kg¹ toapproximately 10 cmol/kg¹.
 13. The vegetative system of claim 1 in whichthe nutritive layer comprises particles having internal micropores. 14.The vegetative system of claim 1 in which the height of the nutritivelayer is between approximately 0.25 inch and approximately 4 inches. 15.The vegetative system of claim 1 in which less than 10% of the particles(by mass) comprising the weed suppression layer will pass through a 3.35mm sieve; between 15% and 50% of the particles (by mass) comprising theweed suppression layer will pass through a 6.3 mm sieve; and at leastapproximately 70% of the particles (by mass) comprising the weedsuppression layer will pass through a 9.5 mm sieve.
 16. The vegetativesystem of claim 1 in which the coarse aggregate particles of the weedsuppression layer comprise crushed brick.
 17. The vegetative system ofclaim 1 in which the height of the weed suppression layer is betweenapproximately 0.5 inch and approximately 2 inches thick.
 18. Avegetative system disposed on a roof of a structure, the vegetativesystem comprising: a water retention layer having a water retentioncapacity, by volume, of at least approximately 60%; and a compositelayer comprising fine organic particles, fine aggregate particles, andcoarse aggregate particles, wherein between approximately 5% andapproximately 25% of the particles (by mass) comprising the compositelayer will pass through a 3.35 mm sieve; between approximately 45% andapproximately 55% of the particles (by mass) comprising the compositelayer will pass through a 6.3 mm sieve; and at least approximately 70%of the particles (by mass) comprising the composite layer will passthrough a 9.5 mm sieve.
 19. The vegetative system of claim 18 in whichless than approximately 2% of the particles (by mass) comprising thecomposite layer will pass through at 0.063 sieve; between approximately3% and approximately 15% of the particles (by mass) comprising thecomposite layer will pass through a 1 mm sieve; and betweenapproximately 5% and approximately 20% of the particles (by mass)comprising the composite layer will pass through a 2 mm sieve.
 20. Thevegetative system of claim 18 in which the water retention layer has awater retention capacity of at least approximately 80% of its volume andwherein the water retention layer retains at least approximately 80% ofthe water retention capacity under 100 pounds of compression.
 21. Thevegetative system of claim 18 in which the water retention layercomprises rock wool having a density in the range of approximately 8pounds per cubic foot to approximately 16 pounds per cubic foot.
 22. Thevegetative system of claim 21 in which the height of the water retentionlayer is between approximately 1 inch and approximately 6 inches and inwhich the height of the composite layer is between approximately 0.75inch and approximately 6 inches.
 23. The vegetative system of claim 22in which the organic matter particles of the composite layer comprisepine fines and in which the fine aggregate particles and the coarseaggregate particles of the composite layer comprise crushed brick. 24.The vegetative system of claim 18 in which the fine aggregate particlesof the composite layer have a cation exchange capacity (CEC) in therange of approximately 6 cmol/kg¹ to approximately 10 cmol/kg¹.
 25. Thevegetative system of claim 18 in which the fine organic particles of thecomposite layer have a cation exchange capacity (CEC) in the range ofapproximately 6 cmol/kg¹ to approximately 10 cmol/kg¹.
 26. Thevegetative system of claim 18 in which the composite layer comprisesparticles having internal micropores.
 27. The vegetative system of claim18 in which the composite layer has a water retention capacity, byvolume, in the range of between approximately 60% and approximately 20%.28. A vegetative system disposed on a roof of a structure, thevegetative system comprising: a water retention layer having depthbetween approximately one inch and approximately three inches, a waterretention capacity, by volume, of at least approximately 80%, and thatretains at least approximately 80% of the water retention capacity under100 pounds of compression; and a bed of material comprising aggregateparticles having a depth between approximately two inches andapproximately four inches wherein between approximately 5% andapproximately 25% of the particles (by mass) will pass through a 3.35 mmsieve, between approximately 45% and approximately 55% of the particles(by mass) will pass through a 6.3 mm sieve; and at least approximately70% of the particles (by mass) will pass through a 9.5 mm sieve.
 29. Thevegetative system of claim 29 in which the bed of material changes as afunction of time; wherein at a first data point between approximately 5%and approximately 25% of the particles (by mass) will pass through a3.35 mm sieve, between approximately 45% and approximately 55% of theparticles (by mass) will pass through a 6.3 mm sieve; and at leastapproximately 70% of the particles (by mass) will pass through a 9.5 mmsieve; wherein at a second data point between approximately 70% andapproximately 100% of the particles in the top one half inch of thematerial will pass through a 12.5 mm sieve but will not pass through a3.35 mm sieve and between approximately 50% and approximately 10% of theparticles in the bottom one half inch of the material will pass througha 6.3 mm sieve but will not pass through a 2 mm sieve; and wherein thetime between the first data point and the second data point is at leastthirty days.
 30. A method of installing a vegetative system disposed ona roof of a structure, the method comprising: installing a waterretention layer having depth between approximately one inch andapproximately three inches, a water retention capacity, by volume, of atleast approximately 80%, and that retains at least approximately 80% ofthe water retention capacity under 100 pounds of compression; installingcoarse aggregate particles to a depth between approximately one inch andapproximately six inches wherein at least approximately 10% of theparticles (by mass) will pass through a 38.1 mm sieve, at leastapproximately 30% of the particles (by mass) will pass through a 5.08 mmsieve; and most of the particles will pass through a 63.5 mm sieve;installing a mixture of fine aggregate and fine organic particles with amass between approximately 10% and approximately 30% of the combinedmass of the coarse aggregate particles, the fine aggregate particles,and the fine organic particles on top of the coarse aggregate particles.